1. Field of the Invention
The present invention relates to a method of processing substrates in a lithography system, and in particular to a method for transferring substrates between substrate preparation units and load lock unit of a lithography system.
2. Description of the Related Art
In the semiconductor industry, an ever increasing desire to manufacture smaller structures with high accuracy and reliability puts great demands on wafer processing technology. In particular, it is important to maximize wafer throughput of wafer processing equipment while maintaining the lowest capital costs and operational costs, and without excessive use of floor space. Floor space in a semiconductor manufacturing environment is expensive, as most space needs to meet high standard clean room conditions. Therefore, the floor space that is to be occupied by wafer processing equipment, i.e. the so-called footprint, is preferably as limited as possible. Furthermore, to ensure that clean room conditions can be maintained, wafer processing equipment is preferably serviced within the clean room.
A very critical step in the manufacturing of integrated circuits on a wafer is lithography. In a lithography process, a predetermined pattern is transferred onto a semiconductor substrate, often referred to as a wafer. Currently, the smallest dimensions of structures patterned with a lithography apparatus are about 70 nm in size. However, to produce even more complex circuits, structures of smaller size are desired.
The throughput of lithography systems is also a critical factor. Charged particle lithography machines are capable of patterning substrates at extremely small dimensions, but at a lower throughput. Currently, optical lithography machines are available which can pattern about 100 wafers per hour. A cluster of 10 charged particle lithography machines, each capable of patterning about 10 wafers per hour, can match this throughput.
The efficient delivery of substrates to be exposed to each lithography machine and retrieval of exposed substrates from each lithography machine is a critical factor in maximizing throughput of the system as a whole.